JPS5943553B2 - Ion exchange membrane, electrode assembly and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an anode for water electrolysis, and more particularly to an electrode catalyst-ion membrane assembly capable of performing water electrolysis at low voltage and a method for manufacturing the same.

Reflecting the recent energy situation, hydrogen is attracting attention from many quarters as a new energy source to replace oil.

Industrial hydrogen production methods can be roughly divided into water electrolysis methods and coke or petroleum gasification methods. Although the former method uses readily available water as a raw material, it requires a large number of electrolytic equipment, is insufficiently adaptable to excess or insufficient current, and suffers from deterioration due to carbonation of the electrolyte and floor space. Many issues remain, including equipment costs. On the other hand, the latter method is generally complicated to operate, requires fairly large equipment, and has problems such as considerable equipment costs. As a means to solve the above problems, a method has recently been proposed in which hydrogen is produced by electrolyzing water in an electrolytic cell using a cation exchange membrane.

The gist of the present invention is particularly directed to a water electrolysis method using such a cation exchange membrane, in which Raney nickel and Raney cobalt ternary alloys are bonded to the cation exchange membrane as an electrode catalyst for the anode.

Generally, nickel, porous nickel, nickel composite oxide, etc. are used as the base metal electrode catalyst.

For example, the patent application filed in 1982-82, which the present inventors have already proposed,
The electrode disclosed in No. 542 has greater effects in terms of lower oxygen overvoltage and durability than previously known electrodes. However, the inventors
As a result of further detailed study, it was discovered that the durability of the above-mentioned electrodes may not necessarily be sufficient, and as a result of diligent efforts to solve this problem, the present invention was discovered. The present invention is also effective in the case of a direct assembly of an electrode catalyst and an ion membrane, since the same drawbacks of a nickel-based catalyst are found.

As already mentioned, so-called SPE water electrolysis, in which water electrolysis is performed by bonding electrode catalysts to each side of an ion membrane, is a new energy-saving hydrogen production method that can replace the conventional method of using asbestos as a diaphragm.

In this type of electrolysis method, the above-mentioned low acid overvoltage anode is preferably used as the anode, but in the above electrolytic operation, the nickel or cobalt of the Raney nickel particles or Raney cobalt particles, which are the electrolytic active ingredients, is converted into nickel hydroxide or hydroxide. It was discovered that the electrode activity deteriorates (that is, the oxygenation voltage increases) due to the deterioration of cobalt, and in order to prevent this deterioration,
It has been discovered that incorporating a third specific component into known metal particles consisting of a first component such as nickel or cobalt and a second component such as aluminum, zinc, magnesium, or silicon brings about a remarkable effect, The present invention has been completed, and the present invention provides a component X1 in which the electrode active metal particles consist of nickel and/or cobalt, aluminum, zinc,
A component Y selected from silicon and magnesium, and a component Z selected from group metals of the periodic table are located at points A and B in Figure 1.
, C, D, and E is an electrode catalyst-ion membrane assembly in which a highly durable low oxygen overvoltage electrode catalyst is bonded to an ion membrane, and in its manufacturing process, it is made of nickel and/or cobalt. Component X1 Component Y selected from aluminum, zinc, magnesium, and silicon and component Z selected from group metals of the periodic table are in the range surrounded by points A', W, C, and K in Figure 2. The gist of the present invention is a method for producing a highly durable ion membrane-electrode catalyst assembly for water electrolysis, characterized in that the electrode-active metal particles made of an alloy are used as an anode and are bonded to the ion membrane by pressure.

Here, FIG. 1 is a three-component diagram of a component X consisting of nickel and/or cobalt, a component Y selected from aluminum, zinc, and magnesium, and a component Z selected from group metals of the periodic table, and is an anode of the present invention. It is necessary that the alloy composition of the metal particles falls within the range surrounded by points A, B, C, D, and E in FIG.

Preferably, the range is F, G, H, and E. Here point F
, G, H are respectively (95, 0, 5
), (85, 10, 5), (46, 10, 44). The effects of the present invention are due to the inclusion of a group metal of the periodic table as one component of the alloy composition, but why does the inclusion of a group metal prevent the formation of hydroxides of nickel or cobalt? The details have not yet been clarified.

However, the inventors of the present invention have found that titanium, tin, and zirconium among group metals are most suitable for achieving the effects of the present invention. That is, when using titanium, tin, and zirconium among Group metals, a low oxygen overvoltage can be maintained for a longer period of time even under more severe environmental conditions. The reason why it is preferable for the metal particles of the anode of the present invention to have a composition surrounded by ABCDE in FIG. 1 is because particles having a composition outside the above range may not be able to maintain a low oxygen overvoltage for a long period of time.

The average particle size of the metal particles mentioned above is also related to the porosity of the electrode surface and the dispersibility of particles during the electrode manufacturing method described below.
A thickness of 0.1 μ to 100 μ is sufficient. Within the above range,
From the viewpoint of porosity of the electrode surface, preferably 0.1 μ to 5
It is 0μ, more preferably 0.1μ to 10μ.

Furthermore, the particles of the present invention are preferably superficially porous in order to achieve a lower oxygen overpotential of the electrode.

Furthermore, it is preferable that the inside of each particle is porous. The degree of porosity is preferably as large as possible; however, excessive porosity lowers the mechanical strength of the particles, so the porosity (POrOsity) should be 20 to 90 (F6
It is preferable to

Within the above range, it is more preferably 35 to 85%, particularly preferably 50 to 80%. Incidentally, the above-mentioned porosity is a value measured by a known water displacement method or nitrogen adsorption method.

Various methods can be used to make it porous, but
For example, a method is preferred in which a part or all of the metal of component Y is removed from an alloy consisting of components X, Y, and Z to make it porous.

In such a case, it is particularly preferable to treat an alloy in which components X, Y, and Z are uniformly blended in predetermined proportions with caustic alkali treatment to remove at least a portion of the metal component Y.

In the case of the membrane-electrode assembly of the present invention, for example, when producing hydrogen by electrolyzing an alkaline aqueous solution, it is not necessarily necessary to treat it with caustic alkali before installing it in an electrolytic cell, and the anolyte used is Because of the caustic alkaline conditions, the metal of component Y is gradually removed during electrolysis and can become the desired anode. Various combinations of compositions of the metal particles can be used, and typical examples include Ni-A1-T.
i, Ni-Al-Sn,. Ni-Zn-Ti, Ni-Z
n-Sn, CO-Al-Ti, CO-Al-Sn, CO
-Zn-Ti, CO-Zn-Sn, Ni-Mg-Ti-
, Ni-Mg-Sn, CO-Mg-TipCO-Mg-
Possible materials include Sn, and even those in which Tl is replaced with Zr. Among these, a particularly preferable combination is Ni-Al-Ti
, CO-AI-Ti, Ni-Al-Zr, CO-Al-
It is Zr.

In the present invention, the alloy particles as described above are bonded onto an ion exchange membrane, but there is no need for this bonding to be particularly limited.
A method such as that disclosed in Japanese Patent No. 2398 is preferably used.

The conditions for such caustic alkali treatment vary depending on the composition of the starting metal particles, but in the case of metal particles having the composition described below, the caustic alkali concentration (NaOH equivalent) is 10 to 100% by weight (NaOH equivalent) of 10 to 35% by weight. It is preferable to immerse it in a ℃ aqueous solution for 0.5 to 30 hours.

The reason for this is that the component Y was selected on the condition that it should be removed as easily as possible, and the component Z should be removed as little as possible. In addition, in the case of the present invention, the metal particles include a component X consisting of nickel and/or cobalt, a component Y selected from aluminum, zinc, and magnesium, and a component Z selected from group metals of the periodic table. N, B',
It is necessary that the alloy be in the range surrounded by C, l)' and E'.

The reason for this is that if it deviates from this range, it may not be possible to secure a sufficient amount of adhesion during the bonding process with the membrane, or even if bonding is possible, the adhesion strength may be low, or the alkali easily soluble metal, that is, the dissolution of component Y. This is because the subsequent activity as an electrode catalyst is not sufficient. Therefore, if there is a slight deviation from the range indicated by Therefore, it can no longer be put to practical use. The thus obtained ionic membrane-electrode catalyst assembly is then treated with caustic alkali (for example, immersed in an aqueous caustic solution) as necessary to elute and remove at least a portion of the metal of component Y in the alloy particles, The particles are rendered porous.

The conditions in such a case are as described above.

In addition, when an alloy of components X, Y, and Z described above is used as particles, it is preferable to perform the caustic alkali treatment as described above, but it is preferable to perform the caustic alkali treatment as described above. It may be attached to an alkaline water electrolyzer to actually perform electrolysis.

In this case, the metal of component Y is eluted during the electrolysis process, and the overvoltage of the electrode is reduced.

However, although the aqueous caustic alkaline solution produced is slightly contaminated by the eluted metal ions of component Y, this generally does not pose a problem. In the case of the present invention, the electrode catalyst used as the cathode is not particularly limited, and may be any of various noble metals that are effective as cathode catalysts, such as ruthenium, rhodium, iridium, platinum, and the like.

Furthermore, a nickel-based electrode catalyst may also be used. These may be directly bonded to the membrane, or an electrode body may be used that is bonded to another core body by various methods such as dipping, chemical plating, electroplating, spraying, etc. . It goes without saying that in this water electrolysis method, it is preferable that the hydrogen overvoltage is as low as possible. Further, as the cation exchange membrane used in the present invention, known fluorine-containing cation exchange membranes can be used, and among them, perfluorinated carbose membranes having carboxylic acid groups as ion exchange groups (e.g., JP-A-51-1989-1) 140899 and JP-A-52-48598) are particularly preferred from the viewpoint of durability and low electrolytic voltage. Next, embodiments of the present invention will be described.

Examples 1 to 11 An alloy powder (500 mesh passes) having the composition shown in Table 1 was prepared, and to 15 g of this, methylcellulose 259 was added and kneaded for 45 minutes, and further cyclohexanol 3CC1
1 CC of cyclohexanone was added) and kneaded for 15 minutes to obtain a catalyst paste.

CF2=CF2 and CF2-CFO(CF2)3C00C
Each of the above alloy powders was coated on one side of a cation exchange membrane made of a copolymer with H3 and having an ion exchange capacity of 1.9 meq/9 resin and a film thickness of 150 µ using a 1.0 η/CTil screen printing machine. On the other side of the ion membrane, separately prepared ruthenium black was applied at 3 my/Cril.

This was then pressed at 150° C. and 250 kg/CTil for 10 minutes. Hydrolysis was carried out at 80°C for 20 hours with a 15% KOH aqueous solution.

Here, a part of the electrode catalyst was peeled off and its composition was decomposed. Next, a Ni mesh was used as a current collector, and the ruthenium black side was used as a cathode at 150°C. )KOH, 11O℃, 100A/Dm
Electrolysis was carried out under the conditions of 2 for 30 days. Table 1 shows the initial oxygen overvoltage of each electrode catalyst, the oxygen overvoltage after 30 days, and the composition of the electrode catalyst after hydrolysis of the ion membrane.

Comparative Examples 1-2 N1-A1 and CO-Al alloy powder in Examples 1-1
It was bonded to the ionic membrane using the same method as used in 1.

A portion of the metal particles on the obtained electrode catalyst-ion membrane assembly was peeled off and its composition was investigated. The same tests as in Examples 1 to 11 were conducted to evaluate performance. Table 2 shows changes in oxygen overflow voltage.
Shown below. Comparative Examples 3 to 9 Electrocatalyst-ion membrane assemblies were produced in the same manner as in Examples except that the composition of the alloy powder was changed to those shown in Comparative Examples 3 to 9 in Table 2.

Claims (1)

[Scope of Claims] 1 Component X consisting of nickel and/or cobalt, component Y selected from aluminum, zinc, silicon, and magnesium, and component Z selected from Group IV metals of the periodic table are located at the points in FIG. An ion exchange membrane and an electrode assembly in which electrode active metal particles made of an alloy in the range surrounded by A, B, C, D, and E are bonded to an ion membrane as an anode. 2 Component X consisting of nickel and/or cobalt, component Y selected from aluminum, zinc, magnesium, silicon, and component Z selected from Group IV metals of the periodic table,
An ion exchange membrane, electrode bonding in which the electrode active metal particles made of an alloy in the range surrounded by points A', B', C', D' and E' in Fig. 2 are pressed and bonded to an ion membrane as an anode. How the body is manufactured.